I would buy it, I think that Clem would make a great protagonist for the next season, but I wouldn't buy it just because she wasn't in it, of course I think most players would want to find out what happened to Clem, but I do think that if they use Clem for the protagonist, they will not start with her, TTG will want to get us thinking and interested so will probably start with a cutscene (maybe interactive) of one or two people somewhere, and then finding their way to the field where Clem is and then Clem sees them but is unsure wether it is Christa or Omid, or just some walkers (which is very unlikely!). I personally think it will carry on as TTG told players to keep their saves... Why else would they if they weren't going to use the old characters?
Anyone, basically I don't think that I would be too annoyed to see Clem not in season 2 although I would want to find out what happened because she is such aN endearing character, who I really grew to love, I thought she was just going to be one of those annoying kids that gets on your nerves until your thinking 'End this now
Enough of me typing, sorry if this is really long